Nichrome wire: characteristics and applications

Modern technology puts serious demands on the indicators of compliance of its composite materials with real working conditions. One of the high-tech alloys is nichrome. Wire and devices containing it, are resistant to aggressive circumstances of functioning.

History of the discovery

The alloy is a compound of nickel with chromium, with variations in the addition of iron, manganese, aluminum, silicium.

Initially, there were two ways of origin. Roots lie in scientific research on the alloying of metals and the modification of their properties. Ni and Cr are the components of high-quality corrosion-resistant and heat-resistant steels.

As a two-component alloy made of nickel and chromium, it was discovered in 1906 in the USA. Today, its various modifications, including three-component based on iron, are used.

Basic properties

The material for modern heating equipment for domestic and industrial use is undoubtedly nichrome wire. Its properties correspond to the highest technological requirements.

1. Specific electrical resistance: within the limits of 1100-1400 Ohm * m.
2. The melting point is about 1400 ° C, which allows it to function at 800-1100 ° C. The maximum permissible value for work depends on the composition. Thus, the iron content reduces it to 850-900 ° C, for a pure two-component it is equal to 1100 ° C.
3. Density: 8000-8500 kg / m3.
4. High strength (σ _в = 650-700 MPa); The indices remain in conditions of acid aggressive environment and significant temperatures.
5. Good ductility, together with an indicative hardness, allows rolling and drawing.

Distinctive characteristics

Among the most demanded electrical products on the market is nichrome wire. The specific resistance of this component of electric heating equipment is extremely high, which makes it possible to have a wide demand.

An important feature of the metal is its resistance to high-temperature oxidation under normal and aggressive conditions. The key role here is played by chrome. The element forms a corresponding oxide film on the surface, which performs a protective function. It is responsible for the corresponding dark color of the material, which is replaced by a characteristic white-gray when the oxidized layer is mechanically removed.

It is worth noting that direct contact with acids still destroys it, even more than corrosion-resistant tungsten.

The two-component alloy has no magnetic characteristics. They arise for multicomponent modifications, but they have weakened indicators.

Nichrome wire is stiff, it does not lend itself to simple force influence.

We systematize information on how to determine the wire nichrome, mainly how to distinguish it from outwardly similar materials:

1. The white color of the new metal, the dark one, was previously worked out.
2. Negative or minimal magnetism.
3. Rigidity.
4. Destruction under the influence of acids, resistance to oxidation under the influence of high temperatures.

Brand nomenclature

Existing brands differ in composition, represent the assortment of alloy nichrome. Wire has a wide use, which is determined by the individual properties of each.

• 1 group - resistor material: Х20Н80, Х20Н73ЮМ-ВИ, Н80ХЮД-ВИ, Х15Н60.
• Group 2 - metal for heating elements for domestic and industrial use with increased characteristics of heat resistance: Х20Н80-Н-ВИ, Х15Н60-Н, ХН70Ю-Н, Х20Н80-Н, ХН20ЮС.
• 3 group - for operation at temperatures up to 900 ° C: Н50К10, Х25Н20.

In this case, the diameter of the nichrome wire of the first group is 0.009-0.4 mm, and for the second - 0.2-7.5 mm.

"Kindred" are cantalou or fechrali - alloys of chromium, aluminum and iron. They are also characterized by high electrical resistance, resistance to heat in the range of 1250-1400 ° C, but lower reliability, albeit low cost (X23Y5S, X13O4, X23Y5S, X27Y5T, X15Y5S).

Explanation of marks

Properties and purpose of products from nichrome are determined by its chemical composition. Consider the main ones.

• Х20Н73ЮМ-ВИ: chrome - 20%, nickel - 73%, aluminum - 3%, molybdenum - 1.5%, manganese - up to 0.3%, titanium - up to 0.05%, iron - 2%, carbon - up to 0.05%; Melted by vacuum-induction method;
• XN70Y-H: Cr-27%, Ni-70%, Al-3%, Mn-up to 0.3%, Cs-up to 0.03%, Ba-up to 0.1%, Fe-up to 1.5% , C - up to 0,1%; Is intended for electric heating elements;
• XH20YC: Cr is 20%, Ni is 20%, Al is 1%, Zn is up to 0.2%, Ca is up to 0.1%, Si is 2.5%, Fe is 50%, C is up to 0, 08% - for heaters of industrial furnaces.

Types of products

The choice of any alloy, which is characterized by high-quality technological and mechanical characteristics, should be justified and regulated. Especially when it comes to high cost. Such high-tech and expensive material is nichrome wire. GOST 8803-89, 12766.1-90, 12766.3-90, 12766.4-90 defines requirements, features of marking and application. In accordance with the standards and depending on the type, the metal is offered for sale in the form of a wire or ribbons, the choice of which depends on the diameter, cross-section, length, features of use.

The corresponding rolling is the starting point for the industrial manufacture of belt zigzags, wire spirals.

Technical specifications

When choosing products from nichrome, it is important to consider the following features:

• Nominal resistivity;
• Diameter, cross-section and weight;
• Actual resistance and operating temperature limits depending on physical parameters.

The nominal values of the basic parametric characteristic are determined by GOST and depend on the brand and composition.

The diameter of the nichrome wire determines its cross-section, the weight of the skein and the corresponding objective resistance.

Thus, the weight of wire (nichrome) per 100 meters of production is directly proportional to its dimensions, and the diameter and cross-sectional area are inversely proportional to the actual resistance.

The operating temperature depends not only on the chemical composition, but also on the parametric characteristics.

The diameter of the wire produced by manufacturers is represented in the range 0.05-12 mm, and the tape - 0.15-3.2 mm.

Application

Quality always justifies the cost. The same applies to alloy nichrome. Wire and tapes of this material are widely used in areas where any other metals could not replace them. High electrical resistance, oxidation resistance, qualitative mechanical characteristics, including for aggressive environments, high-temperature working conditions - all this allows using it in various fields.

In industry:

• Thermocouples of metallurgical electroheating furnaces.
• Structural elements for induction melting equipment.
• Industrial ventilation drying.
• Details of boilers and heat exchangers.
• Electrotechnical production: resistors and rheostats.
• Some electrodes for welding.
• Single-stranded and stranded electrical wires.

It is the main structural element for all modern household appliances:

• Heating elements in electric kettles, boilers, boilers, heaters.
• Heating elements in hair dryers, ploys, irons.
• Automotive candles and heating systems.
• E-cigarettes.

Perhaps the price is the only drawback of the material nichrome. A two-component nickel-chromium wire will be more expensive. The iron content and the reduction in the amount of nickel, in turn, regulate the lower cost, but do not provide those opportunities that X20N80. The choice depends on the technical requirements.

Choosing products from nichrome, it is important to operate with information on the chemical composition of the brand of interest, its electrical conductivity and resistance, the physical characteristics of the diameter, cross-section, length. It is important to be interested in the compliance documentation, and also be able to visually distinguish the alloy from its "competitors". Correctly selected material is a pledge of reliability of technology and technology of its operation.